Field of the Invention
The present invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus each including the electrophotographic photosensitive member.
Description of the Related Art
A surface of an electrophotographic photosensitive member is required to have wear resistance and chemical stability because a stress caused by a series of electrophotographic processes including charging, exposure, development, and transfer, and cleaning as required is repeatedly applied to the surface.
Means for improving the wear resistance of the surface of the electrophotographic photosensitive member is, for example, a method involving incorporating a curable resin into a surface layer of the electrophotographic photosensitive member.
However, when a surface layer having high wear resistance is formed in the electrophotographic photosensitive member, the surface layer hardly wears, and hence a surface of the surface layer is hardly refreshed and chemical deterioration is liable to accumulate on the surface. The chemical deterioration is the one caused by a chemical change of a hole transportable compound (hole transporting substance) owing to the stress generated by the series of electrophotographic processes. The chemical change of the hole transportable compound may be a cause for the occurrence of a phenomenon in which an electrophotographic image output under a high-temperature and high-humidity environment becomes blurred (hereinafter sometimes referred to as “image deletion”).
Therefore, suppression of the image deletion requires suppression of the chemical change of the hole transportable compound.
A technology involving incorporating an additive into the surface layer together with the hole transportable compound is known as a technology for suppressing the chemical change of the hole transportable compound, i.e., improving chemical stability of the hole transportable compound.
Japanese Patent Application Laid-Open No. 2007-11005 discloses a technology for alleviating the image deletion through addition of a specific fluorine atom-containing monomer having a polymerizable functional group to the surface layer.
Japanese Patent Application Laid-Open No. 2007-272191, Japanese Patent Application Laid-Open No. 2007-272192, and Japanese Patent Application Laid-Open No. 2007-279678 each disclose a technology for alleviating the image deletion through addition of a specific amine compound to the surface layer.
Japanese Patent Application Laid-Open No. 2008-70761 discloses a technology for alleviating the image deletion through addition of a specific siloxane compound having a specific polymerizable functional group to the surface layer.
However, the technologies each involving using an additive disclosed in the patent publications are technologies for alleviating the stress on the hole transportable compound and are not technologies for improving the chemical stability of the hole transportable compound itself.
In recent years, an improvement in durability of the electrophotographic photosensitive member has been progressing and hence a demand for additional alleviation of the image deletion has been growing. The alleviation of the image deletion requires not only the alleviation of the stress but also an improvement in chemical stability of the hole transportable compound itself. In addition, the electrophotographic photosensitive member has been required to suppress an image defect in association with occurrence of, for example, a flaw in the surface of the electrophotographic photosensitive member and to satisfy electrical characteristics.